<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        * {
            padding: 0;
            margin: 0 auto;
        }

       
        table {
            border-collapse: collapse;
            border-spacing: 0;
            border: 1px solid #c0c0c0;
            width: 300px;
        }

        th,
        td {
            border: 1px solid #d0d0d0;
            color: #404060;
            padding: 10px;
        }
        th {
            background-color: #09c;
            font: bold 16px "微软雅黑";
            color: blue;
        }


        
        
        

       
    </style>

    <script>

        window.onload = function () {
            //需求1：点击上面的的input，下面全选或者反选。
            //思路：获取了上面的input按钮，只需要判断，checked属性是true还是false，如果是true，下面的全部变成true；false同理。
            //老三步
            var topInp = document.getElementById("theadInp");
            var tbody = document.getElementById("tbody");
            var botInpArr = tbody.getElementsByTagName("input");

            
            topInp.onclick = function () {
                /直接作为下面的所有的input按钮的checked属性值）
                for(var i=0;i<botInpArr.length;i++){
                    botInpArr[i].checked = this.checked;
                }
            }

            
            
            for(var i=0;i<botInpArr.length;i++){
                botInpArr[i].onclick = function () {
                    
                    var bool = true;
                    
                    for(var j=0;j<botInpArr.length;j++){
                        if(botInpArr[j].checked === false){
                            bool = false;
                        }
                    }
                    topInp.checked = bool;
                }
            }
        }

    </script>

</head>
<body>
    <div class="wrap">
        <table>
            <thead>
                <tr>
                    <th>
                        <input type="checkbox" id="theadInp" />
                    </th>
                    <th>菜名</th>
                    <th>饭店</th>
                </tr>
            </thead>
            <tbody id="tbody">
                <tr>
                    <td>
                        <input type="checkbox" />
                    </td>
                    <td>地三鲜</td>
                    <td>田老师</td>
                </tr>
                <tr>
                    <td>
                        <input type="checkbox" />
                    </td>
                    <td>西红柿鸡蛋</td>
                    <td>田老师</td>
                </tr>
                <tr>
                    <td>
                        <input type="checkbox" />
                    </td>
                    <td>醋溜土豆丝</td>
                    <td>田老师</td>
                </tr>
                <tr>
                    <td>
                        <input type="checkbox" />
                    </td>
                    <td>萝卜干炒黄豆儿</td>
                    <td>田老师</td>
                </tr>
            </tbody>
        </table>
    </div>

</body>
</html>